As a method for providing communication infrastructure in places where installation of a wired network is difficult or for securing a communication network speedily at the time of a natural disaster, attention has been directed to a wireless mesh network where wireless access points are interconnected.
FIG. 1 is a diagram showing an example of a configuration of a general wireless mesh network.
As shown in FIG. 1, in the wireless mesh network, terminals 1901 and relay devices 1902 are connected. Each terminal 1901 is a communication device, such as a mobile terminal or a personal computer, which has a function to wirelessly transmit and receive data such as video and audio data. Each relay device 1902 is a wireless access point or the like which has a function to relay, to a receiving terminal, data transmitted by a transmitting terminal.
In the wireless mesh network, communications between the terminals 1901 which cannot establish direct wireless communication with one another can be implemented by establishing communications between the terminals 1901 via one or more relay devices 1902.
However, the wireless mesh network has a problem that as the multi-hop count increases, throughput of traffic communicated between the terminals 1901 decreases.
More specifically, when a relay device 1902 relays received wireless packets to a next relay device 1902, the relayed wireless packets cause interference to neighboring relay devices 1902. This causes packet loss due to collision of wireless packets or delay due to transmission queue.
For this problem, there is a proposed conventional technique for preventing interference of wireless packets transmitted between the relay devices from occurring when two terminals (personal computers) perform communications via two or more relay devices (see Patent Literature 1).
More specifically, as shown in FIG. 2A, Patent Literature 1 discloses a technique in which relay devices 1902 that can directly communicate with one another relay wireless packets by using different frequency channels. For example, frequency channels of 1ch, 3ch, 1ch and 3ch are assigned to the respective relay devices 1902 in the order from left to right in the figure. Thus, it is possible that the frequency channel used for receiving the wireless packets and the frequency channel used for transmitting the wireless packets are different in the respective relay devices. This suppresses occurrence of interference of the wireless packets caused when the respective relay devices 1902 communicate with neighboring relay devices 1902.
[Citation List]
[Patent Literature]
[PTL 1] Japanese Unexamined Patent Application Publication No. 2006-25338